Corvette C5 Modulare Forged Wheel Install

Stop, Drop, And Roll, Part 2: A behind-the-scenes look at how Modulare Forged builds its show-quality three-piece wheels

If you’ve ever wanted to upgrade the wheels and tires on your late-model Corvette, you’re well aware that a lack of options is not a problem. Indeed, the aftermarket is chock-full of choices, with manufacturers offering everything from low-buck replica rims to high-dollar custom units and everything in between. But regardless of your specific performance, aesthetic, and budgetary requirements, finding the right supplier is key to ensuring a successful upgrade.

For our latest wheel project, we teamed up with the pros at Modulare Forged, who were kind enough to walk us through the process of constructing a set of their three-piece wheels. Modulare Forged has been building high-end multi-piece and monoblock (one-piece) rims for nearly 10 years, and in that time the company has established a enviable reputation based on its use of quality materials, interesting designs, and customizable finishes.

Best of all, Modulare designs, builds, finishes, and ships from right here in the United States, and each of its wheels is backed by a two-year limited warranty. More than 30 different designs are available, in diameters ranging from 18 to 24 inches and in a variety of widths to fit almost any chassis. All of the centers are machined and finished to the customer’s specifications, so they’ll fit on almost any Corvette ever built. Just pick a style, send in your specs, and you’ll be up and rolling again in no time.

We had a couple of specific requests on our C5 Z06, and Modulare was happy to accommodate. First off, we needed a wheel that would clear the C6 Z06 brake kit we installed in our last issue. The big, six-piston brakes mandated rims with increased spoke clearance and a larger diameter—a common requirement when upgrading Corvettes in this manner.

Second, we needed a staggered (19-/20-inch) set of wheels compatible with tires that would maintain the C5-specific 0.5-inch tire-height stagger. This would keep the ABS, Competitive Driving, and traction-control systems happy without throwing any trouble codes or putting the Z into “limp home” mode.

We were also looking for a classic design that was both aggressive and modern, to give our Z a timeless look without overpowering the other design elements we’ve come to know and love on the almost-10-year-old body. And finally, we wanted a true three-piece wheel that was built with race-inspired technology for the street, without any compromises.

Follow along now to see how Modulare does it, and then check out the company’s website to find a set that fits your requirements.

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01 The construction of a Modulare Forged three-piece wheel starts here, with a quality T6-6061 forged aluminum blank center. Each blank is inspected by Modulare technicians for flaws or imperfections prior to heading to the lathe. There, the correct profile is cut into the aluminum, after which the center is handed off to the machine center.

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02 Transforming a forged aluminum blank into an actual wheel center takes hours of precision machining, and every Modulare wheel goes through the same process, regardless of the final design. With the blank inserted into the company’s state-of-the-art Haas mill, a technician loads the correct wheel-profile program, and the machining process begins.

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03 Starting in the center, the Haas machine cuts the initial hub bore into the wheel; this will serve as the center for all future cuts and modifications. In a C5 application, the bore is roughly 70.6 mm. Modulare machines a stepped lip into each hub bore, to allow for an O-ringed center cap to be installed later on in the assembly process.

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04 Every step of the way, Modulare technicians check and double check the work of the machines. Here, the depth and alignment of the hub bore are verified before any further work is done to the wheel center. A mistake here would be multiplied over each additional step, resulting in an inferior wheel.

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05 Once the techs are happy with the measurements and alignment of the center bore, the Haas mill is ready to take on the next step: drilling the lug pattern into the wheel center. Both C5 and C6 Corvettes feature a 5x120.65mm (5x4.75-inch) pattern, which is machined for a perfect fitment.

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06 After verifying the bolt pattern is correct, it’s time to begin cutting a pattern into the wheel centers. Modulare has dozens of beautiful designs available, and only you can decide which look is right for you. For this particular build, we chose the company’s M6 model, which is a multi-split-spoke wheel with a modern look.

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07 A lot of aluminum has to come out of the center to achieve the M6 design, and each step requires a different tool to get the job done. The initial cuts are made with a faster bit, and the Haas machine dials up more-precise tooling as it gets closer to the final design.

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08 With the spoke work almost complete, it’s time to drill the outer lip of the wheel center for the bolts that will hold the rim together. As with every other step, precision here is critical, as the bolt holes must align perfectly with both the inner and outer barrels of the final wheel assembly.

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09 We’re not sure what the dollar sign above the top bolt hole means, but we’re guessing it means that these centers look like a million bucks. Notice how the outer lip has been milled with a pocket between the spokes; this reduces weight while also improving looks. At this point, the front of the wheel center is done, but the back still needs to be machined.

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10 This is done by flipping the wheel over and running the remainder of the program. The bore is cut to our 70.6mm specification, and the center of the hub is cut to remove weight. It’s this attention to detail and performance that makes a wheel like this stand out from the crowd.

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11 Once the center is done being machined, it is meticulously inspected by a technician, who hand deburrs each one before giving it the OK and sending it to the finishing department. And that’s just one wheel—we need three more centers just to get the Corvette rolling!

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12 Regardless of the final finish, every wheel center heads to the finishing department, where it is buffed, polished, brushed, or sanded to perfection. Our M6 wheels were ordered with brushed aluminum centers, and Modulare takes the time to brush each one by hand for a perfectly uniform appearance.

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13 Here you can see just how thorough the finishing department really is. Every bolt hole, pocket, and spoke has been worked over by hand to remove any imperfections or harsh edges. The center is brushed to a fine grain, and every surface gets the same treatment to complete the look.

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14 After brushing, the center is sent off to be coated. Ours received a coat of clear powder, which will provide for easy cleaning without covering up the gorgeous brushed appearance. Once the center is back in Modulare’s hands, it’s time to begin the final assembly, which starts with a brushed inner barrel, a chrome outer lip, and the brushed center.

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15 High-strength bolts are used throughout the wheel build, and each one is installed, centered, and torqued by hand. The M6 wheel design takes 39 bolts, each of which features a high-polished look with matching nuts for the inside of the wheel assembly.

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16 The alignment of the inner, outer, and wheel face is absolutely critical, so Modulare techs use a precise rotating fixture to assure that the wheel is perfectly centered and round. With the bolts installed but not tight, the wheel is spun around the fixture and measured. Gentle taps from a mallet perfect the alignment, after which all of the bolts are finally torqued to spec.

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17 Next, a bead of silicone is applied to the inner and outer barrels to prevent air leaks. If you’ve ever owned a set of three-piece wheels that won’t hold air in the tires for a long time, you can thank sloppy machine work, porous aluminum, or a lack of silicone. No such concerns with these beauties!

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18 Finally, it’s time for the machined Modulare center cap to be dropped in place before the wheel is sent to the Quality Control facility. In QC, each wheel is triple checked for perfection, and every aspect of the build is thoroughly examined. The machining, width, offset, bolt pattern, and finish are confirmed, and the wheel is finally ready to ship to the customer.

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19 When the wheels arrived at VETTE’s world headquarters, the quality spoke for itself.

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20 The finish and machine work were second to none…

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21 …and the design had the timeless look that we were after.

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22 No matter how many times the factory checks fitment, it’s up to the car owner to verify that everything is correct before mounting tires to the wheels. Our Modulare M6s fit perfectly in the wheelwells and, more importantly, cleared the massive C6 Z06 brakes we installed in last month’s issue.

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23 The curved M6 spokes housed the big brakes with ease, offering more than enough clearance. This is the advantage of working with a quality wheel builder who understands high-performance building: You get what you need the first time, without any headaches.

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24 Having gone all out on our new wheels, we weren’t about to skimp on a cheap set of matching rubber. Our C5 Z06 is a street driver that sees minimal track time, making the Nitto Invo line an excellent choice. With its 260 treadwear, AA traction, and A temperature ratings, the Invo is billed as an “ultra-high-performance street tire that provides a blend of performance, ride comfort, and quality.”

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25 We ordered our Invos in a 265/30-19 fitment for the front, matching them with a pair of massive 305/25-20 rears. Those specs will maintain our 0.5-inch front-to-rear height stagger (25.31 and 25.94 inches, respectively), which will keep the ABS and TCS happy.

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26 Bolting on the wheels was a simple task, in part because the tight hub bores didn’t require any “hub centric” rings to fit perfectly. The wheels balanced easily, with minimal weights, and we were even able to use the stock lug nuts for a quick-and-easy installation.

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27 Out back, our upsized rolling stock really fills out the wheelwell. Those 305mm Invos should give us plenty of traction under acceleration, and the snazzy chrome lip on our Modulare rims will command attention on the street, ’strip, or show field.

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28 Not surprisingly, the front wheels fit perfectly as well, the 19x9.5-inch M6 wheels really looking at home hugging the fenders. We had plenty of room for the C6 Z06 brakes and gained some rubber width in the process. When all was said and done, our C5 Z06 was sitting pretty and performing better than ever, which is exactly what we were after. vette

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